By agreement reached at the Peace of Venice in 1177 the bitter conflict between Alexander III and Emperor Frederick I was brought to an end.
Eventually, at the Peace of Venice, when Alexander gained victory, he promised Frederick that he would summon an ecumenical council.
Besides removing the remains of the recent schism, the Council condemned the Cathar heresies and pushed for the restoration of ecclesiastical discipline.
William was sent by Baldwin IV as the representative of the Kingdom of Jerusalem, and wrote about the journey to the Council in his history.
His presence was resented by the other archbishops and the lobbying of Duke Henry the Lion of Saxony succeeded in getting his election quashed.